Conventional dredging methods employed in mining typically utilize a spud (which is a vertical pole-like assembly incorporated within the dredge) to anchor the dredge to the bed and sideline winches to slew the dredge clockwise and anticlockwise while it cuts into the ore body.
At the end of each slew, the cutter head is advanced by extending the spud carriage (maximum extension for a spud dredge is 7-10 m). Once the carriage is fully extended, an auxiliary spud is dropped and the main spud raised, allowing the dredge to “walk” forward. Once in the new position, the spud carriage is retracted, the auxiliary spud raised and the main spud dropped allowing mining to continue.
There are a number of drawbacks associated with this type of dredging. Since the spud provides the main reaction force for the cutter, it is not possible to continue mining any virgin area during a spud walk, leading to a typical 5 to 15 minute loss of production with every “walk”. Hence, the continuous mining area for an anchor and spud setting is around 15×50 meters.
The length of the dredge cutter ladder limits the mine width for each spud centerline, as shown in FIG. 1. Hence, for a mine width typically greater than the spud dredge slew arc (typically 50 to 60 meters), it is necessary to have multiple spud centerlines, which also leads to a typical 15 to 60 minute production loss due to the required spud “crab” motion with each centerline change.
Mining-arcs are non-concentric following a spud walk, since the center of the arc and the radius of the arc are changing. This means that unless the slewing speed is controlled to compensate for this effect, the effective cutting rate across the face will be inconsistent.
The heading on a spud dredge is always fixed with respect to the mine face. The heading can not be changed to increase efficiency.
The length and size requirements of the spud increase with the depth of operation, with spud dredge applications typically limited to a maximum mining depth of 22 meters.
There is also a need for complex anchor position planning to ensure sufficient slew forces for the cutter which often requires more anchor moves.
The present disclosure has as one object thereof to overcome substantially the abovementioned problems of the prior art, or to at least provide a useful alternative thereto.
The Applicant has understood and identified that it would be advantageous to provide a new method for the maneuvering of a vessel, such as either a dredge or a stacker used in mining. Such advantages are understood to include, but not be limited to: allowing a dredge to move in a straight line rather than the arcuate movement typical of the prior art; ability to control heading to, inter alia, improve efficiency; improving dredge production availability by minimizing or reducing unproductive downtime due to spud walk and spud crab motion; using a spudless dredge design, the mining area can be improved to at least around 45×200 meters for each set of anchor placements compared to a typical spud dredge mining area of 15×50 meters; for a spud dredge mining a 200 meters wide mine pond, this translates to three spud walks per centerline and three spud crab motions across the pond resulting in more than a one hour loss in production time for every 45×200 meter mining area.
Further advantages include improving and streamlining the cutting trajectory to improve dredging performance, particularly near the pond corner edges, developing a cutting trajectory and cutting sequence that ensures a consistent bite of cut into the ore body, providing a heading that maximizes cutting efficiency, and developing a dredge maneuvering control method that can be used for both shallow and deep operation. It is typically difficult to use spud dredges for depths greater than 22 meters, unless steps are taken to reduce the pond level.
Still further advantages include maximizing the overall production rate by using advanced control techniques to maximize dredge slewing and cutting speed while minimizing cutter trip due to overload, improving the level of automation thus reducing operator input, and formulating an anchor relocation strategy that optimizes the overall production throughput by minimizing the requirements for anchor-move frequency without losing effective available maneuvering forces.
The preceding discussion of the background art is intended to facilitate an understanding of the present disclosure only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.
Throughout the specification and claims, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.
Throughout the specification and claims, unless the context requires otherwise, reference to a “dredge” or variations such as “dredges” or “dredging”, will be understood to include reference to a “vessel”, and vice versa. Similarly, unless the context requires otherwise, reference to either a dredge or vessel, or variations thereof, are to be understood to include reference to a wet concentrator plant, a “stacker”, a “stacker module”, or a module such as may be employed in berthing or docking of a vessel. For example, reference to a dredge is understood to include reference to deep sea dredges and channel dredges. Further, reference to a vessel is understood to include reference to a marine barge, for example.
Throughout the specification and claims, unless the context requires otherwise, reference to one of a “line”, “rope” or “cable”, or variations thereof, is to be understood to include reference to each other term and each should be interpreted inclusively. Further, the term “winch” or variations thereof, unless the context requires otherwise, is to be understood to include reference to any other mechanism by which a vessel may be drawn towards a point remote from that vessel.
Throughout the specification and claims, unless the context requires otherwise, reference to “defined torque”, or variations thereof, is to be understood to refer to a winch that is controlled under a ‘Torque Control mode’ or a winch that has a torque limit when placed under a ‘Speed Control mode’.
Throughout the specification and claims, unless the context requires otherwise, reference to “permissible moving region”, or any variation thereof, is to be understood to include reference to “permissible cutting region”, or vice versa, as may be applicable in the particular context.